WASHINGTON (CNN) --What was once viewed as a premier presidential photo op continues to dog President Bush six months after he landed on an aircraft carrier to declare "one victory" in the war on terrorism and an end to major combat operations in Iraq.

Attention turned Tuesday to a giant "Mission Accomplished" sign that stood behind Bush aboard the USS Abraham Lincoln when he gave the speech May 1.

The president told reporters the sign was put up by the Navy, not the White House.

"I know it was attributed somehow to some ingenious advance man from my staff -- they weren't that ingenious, by the way," the president said Tuesday.

Now his statements are being parsed even further.

Navy and administration sources said that though the banner was the Navy's idea, the White House actually made it.

Bush offered the explanation after being asked whether his speech declaring an end to major combat in Iraq under the "Mission Accomplished" banner was premature, given that U.S. casualties in Iraq since then have surpassed those before it.

During the speech in May, Bush said, "The battle of Iraq is one victory in a war on terror that began on September 11, 2001, and still goes on."

The speech and events surrounding it were widely publicized and served as the symbolic end to the war in Iraq.

At the time, it appeared that every detail of the day's events had been carefully planned, including the president's arrival in the co-pilot's seat of a Navy S-3B Viking after making two flybys of the carrier.

The exterior of the four-seat S-3B Viking was marked with "Navy 1" and "George W. Bush Commander in Chief."

White House spokesman Scott McClellan told CNN that in preparing for the speech, Navy officials on the carrier told Bush aides they wanted a "Mission Accomplished" banner, and the White House agreed to create it.

"We took care of the production of it," McClellan said. "We have people to do those things. But the Navy actually put it up."

The banner has been used by critics of the Bush administration as evidence of bravado and an unclear sense of how dangerous the postwar conflict in Iraq would be.

Assigning responsibility elsewhere, especially to the military, is not a typical move for the Bush administration and raised suspicions among critics.

"The banner signified the successful completion of the ship's deployment," he said, noting the Abraham Lincoln was deployed 290 days, longer than any other nuclear-powered aircraft carrier in history.

At the time of the event, Democrats worried President Bush would use his speech and the dramatic landing for political gain.

On Tuesday, Democratic presidential candidates, hoping to make it a political liability for Bush, accused him of trying to shift blame for the stagecraft to the Navy.

"Landing on an aircraft carrier and saying 'mission accomplished' didn't end a war, and standing in the Rose Garden and stating that 'Iraq is a dangerous place' does nothing to make American troops safer," Sen. John Kerry of Massachusetts said in a written statement Tuesday.

Former Vermont Gov. Howard Dean also issued a critical statement.

"Today, we heard him try to walk away from the USS Abraham Lincoln 'end of major combat operations' announcement, absurdly claiming that the White House was not responsible for the 'Mission Accomplished' banner that decorated the flight deck," Dean said.